1. Field of the Invention
The present invention relates to polyurethane-foam moldings, and more particular to a process, and an apparatus, for producing polyurethane-foam moldings having, at one side thereof, a concave and convex solid contour and which can be advantageously adopted as cushion material in automotive seats.
2. Description of the Prior Art
Heretofore, polyurethane-foam moldings are generally produced with the process comprising of sufficiently mixing polyester and activator, adding tolylenediisocyanate to the mixture, further agitating it into a foamable polyurethane resin reaction mixture, putting this mixture into molds and heating them. Many different formulations for producing polyurethane-foam moldings have been proposed, some of which are, best-known, a formulation of polyester in 100 parts composed of adipic acid in 15 mols, diethylene glucol in 16 mols and trimethylol propane in 1 mol, tolylene diisocyanate in 36 parts and activator in 6 parts, and ones using, as base polymer, other than polyester, namely, polyalkylene ether produced by polymerizing and adding ethylene oxide, propylene oxide and butylene oxide to glycerine or sorbitol. By preparing a foamable polyurethane resin reaction mixture from compounding of diisocyanate and activator with polyester or polyalkylene ether as base polymer, and putting the resin reaction mixture in molds which are so shaped as to provide a desired contour, the polyurethane foam can be molded in a product which has a same contour as desired. In the prior-art process, however, no moldings of intended or desired properties will not possibly be obtained depending upon the mold heating conditions when foaming and curing the foamable polyurethane resin reaction mixture within the molds. This mold heating generally consists of carrying the molds into a hot-air oven, electric oven, infrared-ray oven, or the like kept at a predetermined temperature, and making them stay there for a predetermined period of time. However, such heating ovens are disadvantageous in that it takes a long time to raise the temperature and the temperature distribution is not uniform. Consequently, the molds cannot be evenly heated, and required heating time is long, thus the efficiency of production is low.